Pneumonia - weakened immune system

Definition

Pneumonia is a lung infection that can be caused by many different germs, including bacteria, viruses, and fungi.

This article discusses pneumonia that occurs in a person whose ability to fight infection is greatly reduced because their immune system is weakened and not working properly. Such disease is referred to as "pneumonia in an immunocompromised host."

Alternative Names

Causes, incidence, and risk factors

People whose immune system is not working well are less able to fight off germs. Because of this state, they are more likely to become infected by germs that typically do not cause disease in healthy people. They are also more vulnerable to the usual causes of pneumonia, which can affect anyone.

Signs and tests

The doctor may hear crackles or other abnormal breath sounds when listening to the chest with a stethoscope. Reduced or absent breath sounds can be an important sign, because it may mean there is a buildup of fluid between the chest wall and lung, called a pleural effusion.

Version Info

David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Jatin M. Vyas, PhD, MD, Instructor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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